Hospitals have a large number of mobile physical assets, including gurneys, diagnostic equipment, treatment equipment, bandages and other supplies, drugs, and so forth, as well as physicians, nurses and other personnel that can also be considered mobile assets. Problems arise because it is extremely difficult to keep track of such assets, and it is even more difficult to identify needed assets that may be nearby, but are in a different room, cabinet, or are otherwise hidden from view.
It is known that Radio Frequency Identification Tags (RFID tags) can be used to keep tabs on the locations of equipment, supplies, and so forth, and location information using RFID tags can be quite accurate, down to a few centimeters. It is, however, problematic that RFID tags are usually active over only a very short distance, and therefore commonly require nearby interrogators.
One solution is to distribute a very large number of interrogators within the workspace. In a recent example, Cisco™ announced its Wireless Location Appliance™ 2700, which uses WiFi access points to gather signal strength indicators from 802.11 devices and tags, and triangulates the information to roughly determine the locations of the devices. (See, e.g. http://informationweek.com/story/showArticlejhtml?articleID=162101504). Unfortunately, such systems are problematic because the granularity is poor. Location information is typically accurate only within about 10 meters.
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Another solution is to integrate data captured by separate systems for RFID tag and WiFi technologies. Exavera's™ eShepherd™ operates in that manner, see, e.g. http://www.exavera.com/secure/eShepherd_Overview.pdf. That concept was also described in US patent application publication no. 2004/0217864. In both instances it is contemplated that the devices that interact using RFID tag and WiFi technologies are separate devices. Thus, a doctor may carry a Voice Over Internet Protocol (VoIP) device that provides a signal that can be triangulated using WiFi technologies, and (s)he may carry an RFID access card that is active over only a few centimeters.
A significant problem remains, therefore, that one must trade off accuracy in determining locations with closeness of the monitoring equipment. In a large environment such as a hospital, that tradeoff is unsatisfactory. What is needed are systems and methods that combine RFID and WiFi triangulation technologies in the same device.